add binary exporter to STLExporter
add AI_SWAP4 for big endian architecture
Exporter: if the scene data was converted to verbose format to meet the requirements of a preprocessing step, we should un-verbosify it again before the actual exporter is run.
Exporter.hpp: predeclare IOSystem
Merge branch 'master' of github.com:assimp/assimp
Merge pull request #76 from assimp/fixes

Fixes
Merge pull request #70 from YoheiKakiuchi/master

Add binary exporter to STLExporter
Merge branch 'master' of https://github.com/assimp/assimp into size_t